多环斜孔式喷动流化床内高密度颗粒运动行为的实验和理论研究

The novel spout-fluid bed with multi-ring oblique holes is the specific application of the fluidized bed-chemical vapor deposition(FB-CVD) technique in the particle coating, especially adapted to the preparation of the high-density nuclear fuel coated particles. The main difference between the novel spout-fluid bed and the traditional spouted bed lies in the synergy between holes through the specific design of different annular angle of holes, to achieve uniform contact of the gas-solid phase in a very short time. The project intends to use a combination of experimental measurements and numerical simulation studies to study particle movement behavior. The measurement method will be improved and validated. The impact of the reactor structural parameters and the operating parameters on the particle movement behavior will be investigated. The fluid dynamics mathematical model in the reactor scale of the novel spout-fluid bed will be established. The CFD-DEM coupling mechanism will be studied from the introduction of the source term and the scale effect of gas-solid interaction. The modified CFD-DEM numerical simulation platform will be applicable to simulate the high-density particles fluidization in the complex geometry with strong synergy between holes. The particle motion details and quantitative analysis in particle scale will be obtained, to lay the foundation to scale up the reactor design. Base on the research results, the ideas will be proposed to improve the quality of particle fluidization and increase gas-solid contact efficiency. The research results of this project will provide a theoretical basis of the multiple interacting spout mechanism. It will expand the application of spouted bed technology. The research conclusions of the development of CFD-DEM coupling method have important academic significance, which will develop the multi-scale study of the traditional gas-solid fluidization theory and enhance the capabilities of spouted bed simulation analysis.

多环斜孔式喷动流化床是流化床-化学气相沉积技术在颗粒包覆工艺中的具体应用，尤其适用于核燃料包覆颗粒制备。它与传统喷动床的不同之处在于，通过环状斜孔结构设计，可在极短时间内实现气固均匀接触，获得化学气相沉积的一致性。本项目拟采用实验测量和数值模拟相结合的方法对床内颗粒运动行为进行研究。通过对颗粒流态化特征量的实验测量，考察反应器结构参数、操作参数对颗粒运动行为的影响规律，建立床层尺度环隙区-喷动区流体力学模型。通过考察气固相间作用的尺度效应和源项引入模式，建立适用于复杂几何结构、孔间强协同作用和高密度颗粒流化的CFD-DEM 数值模拟平台，获得颗粒运动行为细节信息，在颗粒尺度上阐明流态化特征量的变化规律和对化学气相沉积的影响，为改进颗粒流化质量和喷动床放大设计提供理论依据。此项目在发展喷动床技术和CFD-DEM耦合理论方面具有重要意义，是非常典型的气固喷动流态化理论多尺度研究的前沿科学问题。

固有安全的第四代核反应堆需要新型的核燃料设计，其中高温气冷堆核燃料制备需要将高密度UO2颗粒流化并均匀包覆起来，因此高密度颗粒在多孔喷动床中的流化状态是影响高温气冷堆核燃料包覆颗粒生产的关键因素。本项目采用实验测量和数值模拟相结合的方法对喷动流化床中颗粒运动和混合行为进行研究。通过对颗粒流态化特征量的实验测量，考察反应器结构参数、操作参数对颗粒运动行为的影响规律，建立喷动流化床流体动力学数学模型。通过考察气固相间作用尺度效应和源项引入模式，建立适用于复杂几何结构、孔间强协同作用和高密度颗粒流化的CFD-DEM 数值模拟平台，获得颗粒运动细节信息，提出新型颗粒混合因子，在单颗粒尺度上阐明流态化特征量的变化规律，为改进流化质量和喷动床放大设计提供理论依据。